1. Field of Invention
The present invention relates, in general, to improving the production efficiency of subterranean wells and, in particular, to a device and method which automatically detects gas locks in an electrical submersible pump assembly (“ESP”).
2. Description of the Prior Art
It is well known that gas lock can occur when an ESP ingests sufficient gas so that the ESP can no longer pump fluid to the surface due to, for example, large gas bubbles in the well fluid. Failure to resolve a gas-locked ESP can result in overheating and premature failure. Conventional practice on an ESP is to set a low threshold on motor current to determine when the pump is in gas lock. When this threshold is crossed, the pump is typically stopped and a restart is not attempted until the fluid column in the production tubing has dissipated through the pump. This wait time represents lost production.
It is also known that there are many methods for determining the proper low current threshold and that an unsatisfactory threshold can result in either damage to the motor or nuisance shut downs.